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    What's the secret to getting fast NVMe speeds?

    Discussion in 'Dell XPS and Studio XPS' started by GaryPitts, Sep 15, 2018.

  1. GaryPitts

    GaryPitts Notebook Geek

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    Bought a Samsung 970 Pro for my XPS 9360. I'm only getting about 1850 MB/s read speed. It's capable of twice that. What is the secret to setting up BIOS and configuring things to get fast speeds? I feel like I just don't have something set up properly.
     
    GaryPitts, Sep 15, 2018
    #1
  2. custom90gt

    custom90gt Doc Mod Super Moderator

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    Sadly I believe it's a limitation of the 9360. I read about this a long time ago and here is a quote from this post:
    "As far as I know both the 9350 and the 9360 with Kaby Lake 7th Gen have 4 PCIe lanes for the M.2. The problem why nobody can get more than 1.8 - 1.9 GBps is that the OPI (interconnection interface for the CPU) is set to GT2 which allows a max speed of 2 GBps and not to GT4 (max. 4 GBps). The most probable reason why Dell does that is that GT2 saves more power that GT4."

    I believe the naming is wrong it it should be OPI 2GT and 4GT respectively. I thought I read about someone figuring out a workaround but I can't find it with a quick search or in my bookmarks.
     
    custom90gt, Sep 15, 2018
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  3. jeremyshaw

    jeremyshaw Big time Idiot

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    @custom90gt It's a power saving mode for the OPI (DMI on package), that basically runs the link at PCIe2 speeds (instead of PCIe3). I remember it cannot be hot switched, so whatever the solution is, it comes down to BIOS changes.

    Also, when did you make moderator!? Congrats, glad to see a real contributor to the community put in position to help even more.


    EDIT: one thing that intrigues me, the new Whiskey Lake U packages now claim 16 PCIe lanes, and the Image Processor is now gone (since nobody ever used it, favoring USB cameras). The IPU used to replace the PCIe controller on the U series chips.

    Basically what I'm getting at, are the extra 4 PCIe lanes on WLU coming from the CPU or the PCH (like the 12 lanes on older U series chips)?
     
    Last edited: Sep 15, 2018
    jeremyshaw, Sep 15, 2018
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  4. custom90gt

    custom90gt Doc Mod Super Moderator

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    @jeremyshaw - I figured it was something for power, although I'm not sure how much power it actually saves? I could have swore I read a post a long time ago about someone who did a bios flag change or something to fix it in his 9360. I sure can't find it now.

    I've been a mod for a short time now, lol. I appreciate the vote of confidence. Thankfully my job here is super easy because we have some really good members.

    That's nice they are doing extra lanes on the U series now. I would hope it's coming from the CPU itself, especially with the IPU out of the picture. I'd be curious for sure.
     
    custom90gt, Sep 15, 2018
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